Add support for calculating the position of the top controls in the cc layer.

cc/top_controls_manager.cc

Index: cc/top_controls_manager.cc
diff --git a/cc/top_controls_manager.cc b/cc/top_controls_manager.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1f3b20e6451a986b936cd92d82d59e22cd48e1c1
--- /dev/null
+++ b/cc/top_controls_manager.cc
@@ -0,0 +1,194 @@
+// Copyright 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cc/top_controls_manager.h"
+
+#include <algorithm>
+
+#include "base/logging.h"
+#include "base/time.h"
+#include "cc/keyframed_animation_curve.h"
+#include "cc/layer_tree_impl.h"
+#include "cc/timing_function.h"
+#include "cc/top_controls_manager_client.h"
+#include "ui/gfx/transform.h"
+#include "ui/gfx/vector2d_f.h"
+
+namespace cc {
+namespace {
+// These constants were chosen empirically for their visually pleasant behavior.
+// Contact tedchoc@chromium.org for questions about changing these values.
+const float kShowHideThreshold = 0.75f;
+const int64 kShowHideMaxDurationMs = 250;
+}
+
+// static
+scoped_ptr<TopControlsManager> TopControlsManager::Create(
+    TopControlsManagerClient* client, float top_controls_height) {
+  return make_scoped_ptr(new TopControlsManager(client, top_controls_height));
+}
+
+TopControlsManager::TopControlsManager(TopControlsManagerClient* client,
+                                       float top_controls_height)
+    : client_(client),
+      is_overlay_mode_(false),
+      top_controls_height_(top_controls_height),
+      controls_top_offset_(0),
+      content_top_offset_(top_controls_height),
+      previous_root_scroll_offset_(0.f),
+      scroll_readjustment_enabled_(false),
+      is_showing_animation_(false) {
+  CHECK(client_);
+}
+
+TopControlsManager::~TopControlsManager() {
+}
+
+void TopControlsManager::UpdateDrawPositions() {
+  if (!RootScrollLayer())
+    return;
+
+  // If the scroll position has changed underneath us (i.e. a javascript
+  // scroll), then simulate a scroll that covers the delta.
+  float scroll_total_y = RootScrollLayerTotalScrollY();
+  if (scroll_readjustment_enabled_
+      && scroll_total_y != previous_root_scroll_offset_) {
+    ScrollBy(gfx::Vector2dF(0, scroll_total_y - previous_root_scroll_offset_));
+    StartAnimationIfNecessary();
+    previous_root_scroll_offset_ = RootScrollLayerTotalScrollY();
+  }
+
+  float offset_top = is_overlay_mode_ ? 0 : content_top_offset_;
+
+  // The two layers that need to be transformed are the clip layer and root
+  // scrollbar layers, which are the only two children of the root layer.
+  LayerImpl* root_layer = client_->activeTree()->RootLayer();
+  for (size_t i = 0; i < root_layer->children().size(); ++i) {
+    LayerImpl* child_layer = root_layer->children()[i];
+    gfx::Transform transform;
+    transform.Translate(0, offset_top);
+    child_layer->setImplTransform(transform);

[wjmaclean, 2013/01/11 14:45:24]

Why are you using the implTransform for this? It's really not what it's intended
for. You should be making these kind of changes to the layer's draw transform
(layer->setTransform()).

[enne (OOO), 2013/01/11 17:20:29]

As I mentioned in
https://codereview.chromium.org/11552009/diff/30001/cc/top_controls_manager.c...,
why are you adjusting the layer tree from the top controls manager? This seems
extremely fragile.

[Ted C, 2013/01/11 17:50:54]

What is the distinction?  I was under the impression that transforms only
applied in the impl thread should use ImplTransforms.  I works with either, but
I couldn't seem to decipher what is the appropriate time to use either.

[Ted C, 2013/01/11 17:50:54]

It needs to move the content/clip layers around somehow though.  This seemed
like the way to best isolate the mutations to just the top controls manager. 
How would you suggest it be done differently?  It certainly could break if the
structure of the impl tree changed, but that is also something we could test
with an integration test (making sure the content actually visibly moves when
exptected).

Previously you mentioned LayerImpls, but I know Alex had reservations about
that.  If I were to insert a new LayerImpl as the only child of the root node
(and reparenting all it's children), then that would give me a layer owned by
this that can easily move around the "world".    But this would get clobbered
with every tree commit and to my understanding would make each commit a much
more expensive operation since the tree structures would be different.

[enne (OOO), 2013/01/11 17:57:01]

Why does it need to move the content/clip layers around? What are you trying to
do? What's the goal here?

From your change description, it sounds like you should be treating the tree
properties as read-only in order to sync the top controls to various tree
properties.

[Ted C, 2013/01/11 18:10:23]

As you scroll down a page, we move the urlbar/top controls off the top of the
screen.  While we are doing this, we need to animate up the content to be
aligned with the moving top controls.

This is all working towards providing fullscreen where the controls move off the
top of the page when you scroll down (and the content fills the viewport) and
you can bring in the controls while in the middle of the page.
I guess my description is invalid then.  It's to provide position of top
controls back to the browser while modifying the rendering tree to align with
the desired positions of the UI controls.

+  }
+
+  // TODO(tedchoc): Adjust fixed position layers as well.
+}
+
+void TopControlsManager::ScrollBegin() {
+  ResetAnimations();
+  scroll_readjustment_enabled_ = false;
+}
+
+gfx::Vector2dF TopControlsManager::ScrollBy(
+    const gfx::Vector2dF pending_delta) {
+  ResetAnimations();
+  return ScrollInternal(pending_delta);
+}
+
+gfx::Vector2dF TopControlsManager::ScrollInternal(
+    const gfx::Vector2dF pending_delta) {
+  float scroll_total_y = RootScrollLayerTotalScrollY();
+  float scroll_delta_y = pending_delta.y();
+
+  float previous_controls_offset = controls_top_offset_;
+  float previous_content_offset = content_top_offset_;
+  bool previous_was_overlay = is_overlay_mode_;
+
+  controls_top_offset_ -= scroll_delta_y;
+  controls_top_offset_ = std::min(
+      std::max(controls_top_offset_, -top_controls_height_), 0.f);
+
+  if (scroll_total_y > 0 || (scroll_total_y == 0
+      && content_top_offset_ < scroll_delta_y)) {
+    is_overlay_mode_ = true;
+    content_top_offset_ = 0;
+  } else if (scroll_total_y <= 0 && (scroll_delta_y < 0
+      || (scroll_delta_y > 0 && content_top_offset_ > 0))) {
+    is_overlay_mode_ = false;
+    content_top_offset_ -= scroll_delta_y;
+  }
+  content_top_offset_ = std::max(
+      std::min(content_top_offset_,
+               controls_top_offset_ + top_controls_height_), 0.f);
+
+  gfx::Vector2dF applied_delta;
+  if (!previous_was_overlay)
+    applied_delta.set_y(previous_content_offset - content_top_offset_);
+
+  if (is_overlay_mode_ != previous_was_overlay
+      || previous_controls_offset != controls_top_offset_
+      || previous_content_offset != content_top_offset_) {
+    client_->setNeedsRedraw();
+    client_->setNeedsUpdateDrawProperties();
+  }
+
+  return pending_delta - applied_delta;
+}
+
+void TopControlsManager::ScrollEnd() {
+  StartAnimationIfNecessary();
+  previous_root_scroll_offset_ = RootScrollLayerTotalScrollY();
+  scroll_readjustment_enabled_ = true;
+}
+
+void TopControlsManager::Animate(base::TimeTicks monotonic_time) {
+  if (!top_controls_animation_ || !RootScrollLayer())
+    return;
+
+  double time = (monotonic_time - base::TimeTicks()).InMillisecondsF();
+  float new_offset = top_controls_animation_->getValue(time);
+  gfx::Vector2dF scroll_vector(0.f, -(new_offset - controls_top_offset_));
+  ScrollInternal(scroll_vector);
+  client_->setNeedsRedraw();
+
+  if ((is_showing_animation_ && new_offset >= 0) ||
+      (!is_showing_animation_ && new_offset <= -top_controls_height_)) {
+    top_controls_animation_.reset();
+    StartAnimationIfNecessary();
+  }
+}
+
+void TopControlsManager::ResetAnimations() {
+  if (top_controls_animation_)
+    top_controls_animation_.reset();
+}
+
+LayerImpl* TopControlsManager::RootScrollLayer() {
+  return client_->activeTree()->root_scroll_layer();
+}
+
+float TopControlsManager::RootScrollLayerTotalScrollY() {
+  LayerImpl* layer = RootScrollLayer();
+  if (!layer)
+    return 0;
+  gfx::Vector2dF scroll_total = layer->scrollOffset() + layer->scrollDelta();
+  return scroll_total.y();
+}
+
+void TopControlsManager::SetupAnimation(bool show_controls) {
+  top_controls_animation_ = KeyframedFloatAnimationCurve::create();
+  double start_time =
+      (base::TimeTicks::Now() - base::TimeTicks()).InMillisecondsF();
+  top_controls_animation_->addKeyframe(
+      FloatKeyframe::create(start_time, controls_top_offset_,
+                            scoped_ptr<TimingFunction>()));
+  float max_ending_offset = (show_controls ? 1 : -1) * top_controls_height_;
+  top_controls_animation_->addKeyframe(
+      FloatKeyframe::create(start_time + kShowHideMaxDurationMs,
+                            controls_top_offset_ + max_ending_offset,
+                            EaseTimingFunction::create()));
+  is_showing_animation_ = show_controls;
+}
+
+void TopControlsManager::StartAnimationIfNecessary() {
+  float scroll_total_y = RootScrollLayerTotalScrollY();
+
+  if (controls_top_offset_ != 0
+      && controls_top_offset_ != -top_controls_height_) {
+    SetupAnimation(
+        controls_top_offset_ >= -(top_controls_height_ * kShowHideThreshold));
+    client_->setNeedsRedraw();
+  }
+}
+
+}  // namespace cc